In general, the procedure for assembling an insulated window structure involves placing one sheet of a glazed structure over another in a fixed,spaced relationship, and then injecting a sealant composition into the space between the two glazed structures, at and along the periphery of the two structures, thereby forming a sandwich-type structure having a sealed air pocket between the structures. In practice, glazed structures are typically glass but can also be plastic. To keep the glazed structures properly spaced apart, a spacer bar is often inserted between the two structures to maintain proper spacing while the sealant composition is injected into place. Also, the spacer bar and sealant can be prefabricated into a solitary unit and after fabrication placed into the space between the glazed structures to form the window structure.
Moisture and organic materials are often trapped inside the sealed air space as a result of the window assembly fabrication process. To minimize the effects of moisture and organic materials trapped in the sealed air pocket, desiccants can be used as a medium to absorb these artifacts. Typically, however, at least some moisture will enter or remain in the sealed air pocket during the time the window assembly is in field service. This use of desiccants prevents moisture from condensing on and fogging interior surface of the glass sheets when the window assembly is in service. Desiccants can be incorporated into the spacer, into the sealant or into the entire unit when the sealant/spacer assembly is a solitary component. Additional desiccants above the amount required to absorb the initial moisture content are included in the spacer/sealant assembly in order to absorb additional moisture entering the window assembly over its service life.
Thermal conductivity in the edge of a window units is typically higher than in the center because thermal energy will less readily pass from glazed structure to glazed structure through the air contained in the sealed air pocket than through the materials comprising the sealant/spacer assemblies known in the art.
Various prior art practices for manufacturing window assemblies are cumbersome, labor intensive or require expensive equipment. An answer to the previously discussed limitations is provided by U.S. Pat. No. 4,431,691, to Greenlee, in which a sealant and spacer strip having a folded or contoured spacer means to maintain the relative distance under compression of glass sheets, wherein the strip comprises a folded or contoured spacer means embedded or enveloped in a deformable sealant. This spacer strip has the advantage of being flexible along its longitudinal axis to enable it to be coiled for storage. The Greenlee assembly is thus a solitary component in which the sealant contains the desiccant.
Greenlee's assembly, while addressing previous limitations does not provide a flat sightline once the glass unit is constructed due to undulations in the spacer after the glazed structure are compressed into place. The sightline in a window is the portion of the spacer/sealant assembly that is viewed through the glass sheets, but is not in contact with these sheets. This flat sightline is desirable to improve aesthetic qualities of installed windows. Also, the Greenlee teaching uses high amounts of sealant material required to envelope the spacer and the folded assembly can be stretched during application as well as along its longitudinal axis. This stretching can also lead to problems in maintaining a flat sightline.